Members of the Rail, Maritime and Transport (RMT) union on Arriva Rail North (Northern) which runs services in Yorkshire, South Western Railway (SWR), Merseyrail and Greater Anglia are staging a walk out for 24 hours following action on Monday and Wednesday.
Picket lines will again be mounted outside railway stations affected by the strike, and passengers face delays, cancellations and replacement buses in some parts of the country.
Northern said it would be running around 1,350 services today, more than half its normal timetable, mostly between 7am and 7pm.
It advises: “As the overall number of trains running will be reduced, we do expect trains and any replacement buses we operate to be extremely busy. Please allow extra time for journeys, plan carefully and consider whether travel is necessary.
“We expect all services to be busy, especially in the morning and evening peak periods, and advise customers to allow extra time to travel.”
Travellers on SWR will have to cope with further disruption this weekend because of engineering work which will affect several routes, with replacement bus services in areas including Southampton, Brockenhurst, Woking and Guildford.
RMT general secretary Mick Cash said: “This week, in the midst of the Tory reshuffle shambles, we called on Transport Secretary Chris Grayling to organise summit talks to move these disputes forwards. We have had no response.
“Mr Grayling’s silence speaks volumes. It is becoming clearer by the minute that all the Tory Government are interested in is protecting the fat profits of the greedy private rail companies regardless of the impact on services and safety.
“The strikes today are about putting public safety before private profit. If RMT can cut deals in Wales and Scotland that guarantee a guard on the trains and which underpin public safety, security and access on our railways, there is no reason we can’t reach the same agreements in England.”
A Department for Transport spokesman said earlier this week: “This is a dispute between a private company and the RMT. However, the Transport Secretary recognises the disruption caused to passengers and has met with union leaders on several occasions, including as recently as December, to help bring an end to the strikes.
“He offered guarantees of employment to members who currently fulfil the role of the second person on the train beyond the length of the franchises.
“Nobody is losing their job as a result of driver-controlled operation trains - employees have been guaranteed jobs and salaries for several years.”
SWR plans to run more than 70 percent of its normal weekday service of 1,700 trains, although there will be rail replacement buses, arrangements to have tickets accepted on other train companies and most routes will see a reduced service.
Greater Anglia plans to run a normal service, with no alterations.
Merseyrail will run a reduced service, mostly between 7am and 7pm, with a break during the middle of the day.
Meanwhile, planned strikes on CrossCountry Trains in a long-running dispute over rostering and Sunday working have been suspended after “significant progress” in talks.
Paul Plummer, chief executive of the Rail Delivery Group, said: “No one wins when strike action disrupts the lives of people trying to get to work, get their children to school or to run their local business.
“Working together we will minimise the impact of the RMT strikes and find a way through this dispute so that we can play our part to support Britain’s economy.”